The present invention relates to a condition monitoring method, in particular to a wind turbine condition monitoring method.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Condition monitoring systems are becoming ever more important in today's wind turbine systems. The condition monitoring system method is capable of preventing wind turbine shutdown on account of premature serious damage, as well as optimizing the maintenance scheme of the wind turbine and preventing erroneous replacement of non-faulty parts. Even in the case of wind turbines on land, condition monitoring systems are becoming indispensable, as without them a wind turbine cannot be certified by the certifying body and is difficult to insure.
However, wind turbine condition monitoring methods in the prior art have the problem of high cost. Customers demand cheap wind turbines, so that wind power can compete with traditional energy sources. However, currently used condition monitoring methods use costly sensors, signal sampling modules and high-performance industrial computers, which form an on-line monitoring point. Thus, in consideration of costs, existing condition monitoring systems only monitor the main drive chain which is most important, abandoning monitoring of the variable pitch propeller and yaw transmission systems. As a result, wind turbine condition monitoring methods in the prior art have the shortcoming that they are unable to comprehensively monitor the main equipment, due to cost limitations.
Hence, if costs are to be prevented from increasing or even reduced when monitoring the entire transmission system of a wind turbine, including the transmission chain, variable pitch propeller and yaw transmission systems, then a new monitoring method must be employed.
Moreover, in the prior art, condition monitoring methods for wind turbines include analysis of signal data such as vibration, acoustics, lubricating oil, generator current signals, temperature and torque.
Vibration analysis is the most widely applied technology in the field of industry on account of its reliability and standardization, and is currently the most commonly used technology in wind turbine condition monitoring. However, since vibration analysis can only monitor those parts of the wind turbine with low rotation speeds, its performance is limited and the system costs are high.
Acoustical analysis is another technology similar to vibration. Acoustical analysis is applicable to low-speed rotation, and is capable of detecting faults at an early stage, but requires an extremely high sampling frequency, which leads to higher costs. Oil/fragment analysis is a commonly used technology in off-line monitoring, used to detect the state of wear of gearwheels and bearings, but is costly when implemented in an on-line system, and is largely unable to monitor bearing defects in a closed-loop oil supply system. Temperature monitoring is another standardized technology, used to avoid operation at high temperature, but it is incapable of further analysis to determine whether or not a rise in temperature is due to a defect. Electric current analysis is mostly seen in academic theses, for the detection of generator faults, for instance open circuits or short circuits, broken rotor bar faults or motor air gap eccentricity, but has been unable to enter industrial application because it has a low signal-to-noise ratio, is unable to achieve early-stage fault detection and has a limited application scope. Torque measurement is still in the research stage and has a high cost, and is unable to monitor an entire transmission chain.
Thus, wind turbine transmission monitoring methods in the prior art are not applicable to variable pitch propeller and yaw systems of wind turbines; a new, economical and effective monitoring method is required.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved wind turbine transmission monitoring method which can be used with variable pitch propeller and yaw systems and which is economical to implement.